The present invention relates to laser marking systems that place markings onto products by emitting a laser beam.
Marking systems are used to place informative markings on products, typically during their manufacture and/or distribution. Informative markings include useful information about the product; for example, an expiration date, xe2x80x9cborn-onxe2x80x9d date or date of manufacture, lot number, place of manufacture, and the like.
Laser-marking systems use a laser to place informative markings on products. A laser emits a laser beam that is directed to the product to etch informative markings onto the product. The laser beam may etch the surface of the product or a coating placed on the product beforehand. At times, laser-marking technology has certain advantages over other marking technologies, e.g., ink jet printing technology. For example, the maintenance of a laser equipment may be easier and more economical in certain circumstances than the maintenance of other types of markers. Since the laser marking technology does not depend on the use of an ink in a liquid state to produce a mark, it is less prone to printing problems caused by ink.
In addition, laser-marking technology allows marking of substrates at extremely high speeds. An example of the use of this technology is in the marking of expiration dates on plastic soda bottles. During laser marking, the rate of movement of the conveyor carrying the soda bottles generally ranges from about 100 to 300 feet per minute, and it can be as high as 500 feet per minute.
It is important that laser-marking systems place informative markings onto products with a high rate of reliability. If products are not marked properly, such products may leave manufacturing and/or distribution facilities without the desired informative markings. When products moving at high speeds on an assembly line are marked, a product indicator may be used to detect the products as they pass in front of a marking laser. The laser emits a laser beam in response to a signal generated by the product indicator so that the laser beam is automatically emitted so as to precisely mark each product.
Occasionally, the marking laser may fail to emit a laser beam due to a malfunction or other problem. For example, the laser may have a dirty lens or other object blocking the laser beam path. However, in the event of such failure, the product indicator continues to detect products and trigger the laser to emit a laser beam. Absent some countermeasure, the laser-marking system will not detect a laser that is failing to emit a laser beam and mark products, and products will continue to move past the laser-marking system on the assembly line, potentially leaving the manufacturing and/or distribution facilities without the desired informative markings.
The present invention relates to a laser-marking device and system that determines if a laser beam has been emitted in proper relation to a detected product. A product indicator produces a signal when it either detects a product in proximity to a marking laser or is expecting a product to be in proximity to a marking laser. The marking laser emits a laser beam to place informative markings onto the product in response to this signal. A laser beam detector is placed in range of the laser beam to detect if the laser beam was emitted in proper relation to a signal from the product indicator. If the laser beam was not emitted in proper relation to the signal from the product indicator, an error output signal is generated.
In one laser beam detector embodiment, the laser beam detector is a thermal sensor that detects a temperature change (i.e. the presence or absence of heat). The thermal sensor is placed in proximity to the laser beam emitted by the laser-marking device.
In a second laser beam detector embodiment, the laser beam detector is comprised of an infrared emitter and detector. The infrared emitter and detector are placed on opposites sides of the laser beam path. If the infrared signal is passed through a laser beam, the infrared detector can detect a change in the infrared signal and generate a laser beam detection signal in response thereto. As one of ordinary skill in the art will appreciate, this embodiment may also be implemented by using a combination infrared emitter and detector wherein the emitter and detector reside in the same structure located on one side of the laser beam path.
In a third laser beam detector embodiment, the laser beam detector is a laser detector. The laser beam detector is placed in the expected path of the laser beam. Laser detector generates a laser beam detection signal in response thereto.
In a fourth laser beam detector embodiment, the laser beam detector is a thermocouple device. The thermocouple device is a thermocouple attached to a glass window placed in the expected path of the laser beam. The thermocouple detects a change in heat of the glass window as the laser beam passes through the window and generates a laser beam detection signal in response thereto.
In a fifth laser beam detector embodiment, the laser beam detector is a sonic emitter and detector. The sonic emitter and detector are placed in the path of the laser beam, and the sonic emitter emits sounds waves towards the detector. The sonic detector can detect whether sound waves passed through the laser beam, and in response generate a laser beam detection signal.
A controller may be provided to determine if a laser has emitted a laser beam in proper relation to a product. The controller may include electronic circuitry, a micro-controller, or a microprocessor. The controller may also include memory, counters, and/or timers.
In one controller embodiment, a product indicator emits a product indication signal. A counter counts the product indication signals received and outputs the count into a flip-flop. The laser beam detector emits a laser beam detection signal when the laser beam is detected. If more than a selected amount of products are detected by the product indication signal without the laser beam detection signal resetting the counter and/or flip-flop, the flip-flop changes states and emits an error output signal to signify that the laser beam did not mark a product.
In a second controller embodiment, the product indication signal and laser beam detection signal are input into a first and second counter in the controller, respectively. The first counter counts the number of products detected, and the second counter counts the number of laser beams emitted by the laser. A microprocessor in the controller compares the first counter and the second counter. If the values of the first and second counters differ by more than a threshold amount, the microprocessor generates an error output signal to signify that the laser beam did not mark a product(s).
In a third controller embodiment, a microprocessor in the controller uses a timer to record the time of receipt of both the product indication signal and the laser beam detection signal. The microprocessor determines if the time between the receipt of the product indication signal and the laser beam detection signal is greater than a threshold time value. If the time difference is greater than a threshold time value, the microprocessor generates an error output signal to signify that the laser beam did not mark a product(s).
The laser beam detection signal may also be coupled to a customer interface. The error output signal may also be coupled to a customer interface. The customer interface may include a counter to count the number of laser beam detection signals received. The value of this counter indicates the number of products marked with informative markings by the laser.
Alternatively, the product indication signal and the error output signal may also be coupled to a customer interface. The customer interface may include a counter to count the number of product indication signals received. The value of this counter indicates the number of products marked with informative markings by the laser, provided an error output signal is not received by the customer interface. The customer interface may also subtract the count of the error output signal counter from the count of the product indication signal counter to determine the number of products marked with informative markings by the laser.
The error output signal may also be coupled to (1) a central controller that operates an assembly line transporting products through the laser-marking system and/or (2) the laser-marking system itself. If the central controller receives an error output signal, the central controller may stop the assembly line, stop the laser-marking system, alter the operation of either the assembly line or the laser-marking system, generate an alarm condition, and/or communicate the error output signal over a network to a remote system.
After the detection of an error output signal, the customer interface and/or central controller may also be designed to restart the assembly line after a reset indicator, located at the customer interface or at a remote location, is activated either manually by a user, in response to another system, and/or on the next valid laser-marking made onto a product.